A method and device to avoid collision on opening of a vehicle door is shown in DE 10 2005 014 581 A1. The objective of the device is to prevent an approaching obstacle from coming into contact with the vehicle door. To achieve this, the device proposes a proximity sensor, which detects approach of a hand to the inner door handle of the vehicle. Monitoring of a vehicle environment for approaching obstacles is triggered on this account. In the event that an obstacle is found, the device issues a warning signal for an occupant of the vehicle, so that he refrains from opening the vehicle door. A drawback here has been that, despite acoustic or optical warning, the door can be opened. The described device therefore does not prevent the occurrence of undesired accidents.